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Jesionek P, Hachuła B, Heczko D, Lamrani T, Jurkiewicz K, Tarnacka M, Książek M, Kamiński K, Kamińska E. Studies on the nature and pressure evolution of phase transitions in 1-adamantylamine and 1-adamantanol. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 299:122794. [PMID: 37167743 DOI: 10.1016/j.saa.2023.122794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 04/01/2023] [Accepted: 04/26/2023] [Indexed: 05/13/2023]
Abstract
In this paper, several experimental techniques, i.e., differential scanning calorimetry, X-ray diffraction, Fourier transform infrared, Raman, and broadband dielectric spectroscopy were applied to study the nature of the phase transitions in 1-adamantylamine (1-NH2-ADM, C10H17N) and 1-adamantanol (1-OH-ADM, C10H16O). Calorimetric measurements showed one and three endothermic peaks in thermograms for the latter and the former substance, respectively. Indeed, results of spectroscopic investigations indicated that the observed thermal events in 1-NH2-ADM correspond to transitions between various plastic crystal (PC) phases (I, II, III, IV), while the endothermic process in 1-OH-ADM can be assigned to a phase transition between the PC and the ordinary crystal (OC). Especially interesting were the outcomes of dielectric studies carried out both at ambient and high-pressure conditions, during heating and cooling cycles. They showed: i) noticeable changes in the frequency dependencies of the imaginary (ε'') and real (ε') parts of the complex dielectric permittivity that occurred around temperatures of the characteristic endothermic events detected by the calorimetry, and ii) significant fluctuations of ε'' and ε' at pressures attributed to the respective phase transitions. Moreover, the pressure coefficients of the phase transition temperatures were estimated to be approximately equal to 0.2 K/MPa for both compounds. In turn, volume variation (ΔV) at the PC (II)-PC (III) and PC (III)-PC (IV) transition temperatures for 1-NH2-ADM was essentially different than ΔV for the PC-OC transition in 1-OH-ADM.
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Affiliation(s)
- Paulina Jesionek
- Institute of Chemistry, Faculty of Science and Technology, University of Silesia in Katowice, Szkolna 9, 40-007 Katowice, Poland; Department of Pharmacognosy and Phytochemistry, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, Jagiellonska 4, 41-200 Sosnowiec, Poland
| | - Barbara Hachuła
- Institute of Chemistry, Faculty of Science and Technology, University of Silesia in Katowice, Szkolna 9, 40-007 Katowice, Poland.
| | - Dawid Heczko
- Department of Statistics, Department of Instrumental Analysis, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, ul. Ostrogorska 30, 41-200 Sosnowiec, Poland
| | - Taoufik Lamrani
- Institute of Physics, Faculty of Science and Technology, University of Silesia in Katowice, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland
| | - Karolina Jurkiewicz
- Institute of Physics, Faculty of Science and Technology, University of Silesia in Katowice, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.
| | - Magdalena Tarnacka
- Institute of Physics, Faculty of Science and Technology, University of Silesia in Katowice, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland
| | - Maria Książek
- Institute of Physics, Faculty of Science and Technology, University of Silesia in Katowice, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland
| | - Kamil Kamiński
- Institute of Physics, Faculty of Science and Technology, University of Silesia in Katowice, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland
| | - Ewa Kamińska
- Department of Pharmacognosy and Phytochemistry, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, Jagiellonska 4, 41-200 Sosnowiec, Poland
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Okay O. Re-Entrant Conformation Transition in Hydrogels. Gels 2021; 7:gels7030098. [PMID: 34287329 PMCID: PMC8293105 DOI: 10.3390/gels7030098] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/09/2021] [Accepted: 07/13/2021] [Indexed: 12/20/2022] Open
Abstract
Hydrogels are attractive materials not only for their tremendous applications but also for theoretical studies as they provide macroscopic monitoring of the conformation change of polymer chains. The pioneering theoretical work of Dusek predicting the discontinuous volume phase transition in gels followed by the experimental observation of Tanaka opened up a new area, called smart hydrogels, in the gel science. Many ionic hydrogels exhibit a discontinuous volume phase transition due to the change of the polymer-solvent interaction parameter χ depending on the external stimuli such as temperature, pH, composition of the solvent, etc. The observation of a discontinuous volume phase transition in nonionic hydrogels or organogels is still a challenging task as it requires a polymer-solvent system with a strong polymer concentration dependent χ parameter. Such an observation may open up the use of organogels as smart and hydrophobic soft materials. The re-entrant phenomenon first observed by Tanaka is another characteristic of stimuli responsive hydrogels in which they are frustrated between the swollen and collapsed states in a given solvent mixture. Thus, the hydrogel first collapses and then reswells if an environmental parameter is continuously increased. The re-entrant phenomenon of hydrogels in water-cosolvent mixtures is due to the competitive hydrogen-bonding and hydrophobic interactions leading to flow-in and flow-out of the cosolvent molecules through the hydrogel moving boundary as the composition of the solvent mixture is varied. The experimental results reviewed here show that a re-entrant conformation transition in hydrogels requires a hydrophobically modified hydrophilic network, and a moderate hydrogen-bonding cosolvent having competitive attractions with water and polymer. The re-entrant phenomenon may widen the applications of the hydrogels in mechanochemical transducers, switches, memories, and sensors.
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Affiliation(s)
- Oguz Okay
- Department of Chemistry, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey
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